Among the simple diatomic molecules, oxygen is of particular interest because it shows magnetism at low temperatures. Moreover, at pressures exceeding 95 GPa (ϳ0.95 Mbar), solid molecular oxygen becomes metallic, accompanied by a structural transition 1 . The metallization process is characterized by an increase in optical reflectivity 2 , and a change in the slope of the resistance-

We have measured electrical resistance of oxygen under high pressures up to 120 GPa and at temperatures down to 45 mK.

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